Electrical control system



Aug. 17, 1948. o. E. BowLus ELECTRICAL CONTROL SYSTEM 2 sheets-sheet 1 Filed July l0, 1946 Aug. 17, 1948. o. E. BowLus ELECTRICAL CONTROL SYSTEM 2 sheets-Sheet 2 Filed July l0, 1946 1N V EN TOR. Ome? E.' .25am/Z215 /77' Top/VE V5.

Patented Aug. 17, 1948 ELECTRICAL CONTROL SYSTEM Omer E. Bowlus,

Detroit, Mich.,

assignor to Chrysler Corporation, Highland Park, Mich., a

corporation of Delaware Application July 10, 1946, Serial No. 682,485

21 claims. 1

The present invention relates to electrical control systems and is particularly directed to the provision of improved apparatus which functions as a combination converter-inverter for transferring alternating current energy from a source of alternating current to an output alternating current system of a desired frequency, the frequency whereof and phases whereof may be equal to, less than, or greater than the number of phases and the frequency of an alternating current input system.

The principal objects of the present invention are to provide a system of the aforesaid type which is simple in arrangement, requires a minimum number of control elements, is relatively light in weight, and is reliable and efhcient in operation; to provide such a system in which electronic valves are used to control the flow of energy between the input and output system; to provide such a system in which the cathodes of the electronic means supplying each phase of the output circuit may be electrically connected together; to provide in such lan electronically controlled system a circuit whereby all of the cathodes of all of the electronic means may be tied together and may be grounded; and generally to improve and simplify the construction and arrangement of systems of the above generally indicated type.

With the above, as well as other-and more detailed objects in View, which appear in the following description and in the appended claims, preferred but illustrative embodiments of the invention are shown in the accompanying drawings throughout the several views of which corresponding reference characters are used to designate corresponding parts, and in which Fig. l is a diagrammatic view of an embodiment of the invention, and

Fig. 2 is a diagrammatic view of a modification of the invention.

Referring to the drawing by characters of reference, numeral I indicates generally a threephase power source which may be supplied from a transmission line, an inductive generating means, or other means by which electrical energy is induced in three electrically isolated Y-connected or star-connected three-phase systems 2, 3. and 4. The secondary system 2 comprises phase windings 2A, 2B, and 2C having a comm-on point 2D. Likewise, the secondary systems 3 and 4 comprise respectively phase windings 3A, 3B, and 3C connected together at a common point 3D and phase windings 4A, 4B, and 4C connected z together to a common point 4D. Groups of elec-` tronic valves 6, 8, and I0 are associated respectively with the input systems 2, 3, and 4. Each group of electronic valves 6, 8, and I0 comprise six individual electronic valves A, B, C, D, E, and F which, for the purpose of easy identification, are prexed by the numeral designating the group to which they belong; for example, 6A, 6B, 6C, 6D, 6E, and 6F. Each of the electronic valves of groups 6, 8, and I0 includes an anode, a cathode, and a grid, and are preferably of the gas-filled type in which the grid is ineffective to control flow of current through the valve after the valve has once been rendered conductive. Each of the group of valve means 6, 8, and I I] may be considered as being further subdivided into a pair of valve means units comprising the valves A, B, and C as one unit and the valves D, E, and F the other of the valve means unit.

Transformer units I2, I4, and I6 are associated respectively with the valve groups 6, 8, and I0. Each of these transformer units I2, I4, and I5 comprises three primary coils A, B, and C and a secondary or output coil O. The coils for each of the transformer units `are prefixed with the numeral designating the transformer unit for convenience. Each of the coils A, B, and C has end connections and a center tap connection and is wound about a single iron core whereby current owing through any of the coils A, B, and C will set up a iiuX in the core of the respective transformer unit I2, I4, or I6. The anodes of the valves A, B, and C are connected respectively to corresponding end connections of the primary coils A, B, and C of the transformer units with which the groups of valves are associated. Likewise, the anodes of the valves D, E, and F are connected to the opposite corresponding end connections of the transformer primary coils A, B, and C. Commutating condensers CI are connected between the end connections of the coils A, B, and C of the transformer units I2, I4, and I6.

The center tap connection of the primary coils IZA, IZB, and I2C are connected respectively by conductors I8, 20, and 22 to the noncommon or outward ends of the windings 2A, 2B, and 2C respectively of the system 2. likewise the center tap connection of the coils I4A, MB, and I4C are connected by conductors 24, 26, and 28 to the noncommon or outward ends of the windings 3A, 3B. and 3C of system 3. The center tap connections of the coils IBA, ISB, and IBC are also similarly connected by means of conductors 3U, 32, and 3i to the noncommon or outward ends of the windings 4A, 4B, and 4C of the system 4.

All the cathodes of the various electronic valves of the units E, 8, and Iii are connected together to a common conductor or bus bar 35, which bus bar 36 is connected by means of conductors dit, 46, and 4S to the common points 2D, 3D, and eD of the systems 2, 3, and l respectively. Interposed in series in the conductors All, Q6, and 48 are 'inductive reactors 2R, 3R, and IR respectively. Bus bar 36 is also connected by means of conductors 38, lli), and i2 to corresponding end connections of the secondary coils O of the transformer units I2, I4, and I6. The opposite corre-- sponding end connections of the output coils lf2-IJ, Iii-I3, and IIiare connected -to output conductors 50, 52,1and 54 respectively which constitute the output circuit of the converter-inverter system. The grids of the valves A, B, and C of the valve group 6 are connected through resistors RI to a common grid connection B. The grids of the valves D, E, and F of the valve group 5 are lconnected through resistors R2 to a common grid connection 58. Likewise .the grids of the corresponding valves kof the valve groups 8 land IIJ are connected Vsimilarly through resistors RI and R2, to rcommon grid connections Eil and G52 for group 8 zand and 65 for group IIl.

When a grid bias voltage is applied between the bus bar `3S and `the common grid conductor 56, such that the grids o1"v the valves A, B, and C connected thereto .are rendered positive with respect tothe cathodes of these valves A, B, and C, some of the an-odes of the valves 56A, lEB, or 6C will be at a positive potential with respect to the potential of the bus 4Ioar 36 to which all the cathodes are connected and such of the valves 5A, 5B, and '8C will be vrendered conductive. When valve 6A conducts, current will flow from the winding 2A through conductor I8 through the left-hand portion of coil I 2A through the valve '5A to the bus Current will ralso flow periodically from the windings 2B and 2C through conductors 29 and 2.2 and the left-hand portion of coils IZB and I2C through the valves '6B vand EC to the bus 35. From the bus 35 the current flows through conductor itl and reactor 2R to the common point of the system 2D. The current in each of the conductors I3, 20, .and 2:2 wi-ll of course iow periodically when the anodes are positive and vary proportionally to actor y2R to the common point 2D. Current flow through the right-hand half of the coils IZA, IZB, and I2C will set up a flux in the iron of the transformer unit I2 in a direction opposite to the direction of the flux set up when the left-hand half of these coils are conducting, and reverse the linx cutting the coil IZ-Il to induce a voltage therein of the opposite polarity. It may be seen, theretore, that the rapidity with which the common Vgrid connections 5S and 53 are alternately rendered positive and negative with respect to the 36 will determine the frequency of the output voltage oi the `output coil yI 2 9.

The common grid connections @ii and 52 of the valve group ii and the common grid connections 64 and- (i5 of the valve group It! are likewise alv ternately and periodically rendered. positive and the voltage zacross the windings 2A, 2B, and 2C.

This flow of ycurrent through the rcoils I 2A, I'ZB, and I 2C will set up ya -ux inthe iron of the transformer -unit .I2 which will induce a voltage into the output coil I:2-.0 of given polarity.

`4Subsequently the grids of the valves 5D, 5E, and 6F will be rendered positive with respect to the bus bar 36, and, at the same time, the grids of the valves A, 15B, .and `IiIC will he rendered negative with respect to the potential of the `bus 316. As soon as .the current flowing through .the valves 5A, 6B, and 5C is brought `to zero as a result of the action of the commutating .condenserCI Ylater to be described, vin whichever .of the valves SA, iiB, and 6C happen to be conducting .at the time the grids of these valves are rendered negative with respect to their cathodes, Vthe valves Will cease to conduct and will remain in a nonconductive state until their grids are again rendered .positive with respect to vtheir cathodes. The rendering of the grids of the valves D, "5E, and 5F positive will cause the valves to become conductive and current will flow periodically vfrom .the windings 2A, 2B, and 2C through conductors I3, 20, and 22 and the right-hand half of the primary coils II2A, IZB, and I2C, through the valves iiD, EE, .and 6F 4to the bus 36 and return through the conductor 44 and renega-tive with respect to the common bus '38, and so that an alternating voltage is induced in the secondary coils 4III-t2# and Iii-0. It will `he noted that these coils are connected in star or Y connection so that if the common grid connections 56, 6E, Si), .513, till, and $2 are sequentially rendered positivo and negative in that order, a three-phase output will be had. inthe output conductors 5B, e2, and. 5d ofthe frequency ofthe alternate rendering oi' each pair of the common grid connections positive and negative.

This alternaterendering-of .the pairsl of common grid connections -53, {3Q-6.2, and 6d-5G positive and negative is controlled by a timing system generally designated Idil. The system Iilil cornprises electronic valves I'IlZ, Idil, Iil, IEIB, IIB, and I I2 respectively foreach of the common grid connections 55, 53, l, S2, 613, and 66 and a master oscillating valve IM which is adjusted to oscillate at a frequency which is six times the irequency of 4the output circuit 5I), 52, Iand '54. The control circuit for the valves IIlZ, HM, ISB, Hi8, IIl,

, and I'I2 is so arranged that for each cycle of the oscillating valve IIli a nonconducting valve is rendered conductive, one of the valves which was conducting is rendered nonconductive and another of the valves which was nonconducting is primed (rendered in condition s-o that upon the next `oscillation of the oscillator valve IM it Will become conductive). 'At the next cycle of the valve IIA! another valve will be rendered conductive, another valve will be render-ed nonconductive, and still another valve will be prime-d, and so on for each cycle of valve IM. Three of the Valves E532, IEM, I, ISS, II, and IIZ will be con-` ductive at one time. Assuming the three conductive valves to be valves IIM, IUS, and IIQ, at the next cycle of the oscillator valve I I, valve Ili'.'

will be ren-dered conductive, valve IM will be rendered nonconductive, and valve IIIZ will be primed. At the next oscillation of the valve Ili the valve IIlZ will be rendered conductive, valve I I@ will. be rendered nonconductive, and valve I will be primed. 'Ihe valves will be primed, rendered con-ductive, and rendered nonconductive in the following order: M32, II2, m6, Idd, IIt, and IDS with each valve being conductive for three cycles of the valve II Il and nonconductive for three cycles.

Referring more specically to the various elements and circuit arrangements of the unit Idil,

. the valve I I'l is Iof the triode type having an anode,

l of a transformer I I6 having its primary coil energized, for example, from a convenient one hundred ten-volt, sixty-cycle source. The cathode of the valve H4 is connected through a resistance R3 and a condenser C3 to a ground terminal Gl, the grid is also connected through a resistance R4 to the same ground terminal Gl. The anode of the valve H4 is connected to one terminal of the primary coil of a transformer T2 which has its other terminal connected to a potential source BI such as a battery having its other terminal connected to the ground terminal Gl. One terminal of the secondary coil of transformer T2 is directly connected to the ground terminal GI and the other terminal of the secondary coil of transformer T2 is connected to a grid supplying bus H8 which is connected to each of the grids of the valves |02, |04, |06, |08, H0, and H2 through condensers C4 and resistors R4 arranged in series circuit. The terminal of the secondary coil of transformer T2 which is connected to the ground terminal Gi is also connected to a cathode bus |20. Each of the cathodes of valves |02, |04, |06, |08, H0, and H2 is connected to the bus |20 through a resistor R5. A second D. C. potential is applied by a suitable means, 'such as a battery, between the ground terminal GI and a terminal B2 which is negative with respect to the ground terminal GI. The potentiometer resistor PRI is connected between the terminals Gl' and B2 and has an adjustable potential terminal |22. A bus |24 is connected to the adjustable terminal |22 and to each of the cathodes of the valves |02, |64, |06, |08, H0, and H2 through resistors R6 and R1 arranged in series. A conductor |26 having a resistor R8 in series therewith connects the junction between the resistor R4 and the condenser C4 associated with the valve |02 to the junction between the resistor R6 and the resistor Rl associated with the valveV |08. A conductor |28 having a resistor R9 in series therewith connects the junction between the condenser C4 and the resistor R4 associated with the valve |04 to the junction between the resistors R6 and R1 associated with the valve |06. A conductor |30 having a resistor Rl 0 in series therewith similarly connect the junction between the condenser C4 and the resistor R4 associated with the valve |06 to the junction between the resi-stor R6 and Rl associated with the valve H2. Alsosimilarly a conductor |32 having a resistor RH in series therewith connects the junction between the condenser C4 and the resistor R4 associated with the valve |08 to the junction of the resistor R6 and the resistor Rl associated with the valve I0. A conductor |34 having the resistor R|2 connects the junction between the resistor R4 and the condenser C4 associated with the valve H0 to the junction between the resistor R6 and the resistor Rl associated with the valve |04. A conductor |36 having a resistor R|'3 in series therewith connects the junction between the resistor R4 and the condenser C4 associated with the valve H2 to the junction between the resistor R6 and the resistor Rl associated with the valve |02. The heaters for each of the valves |02l |04, |06, |03, l0, and l2, as indicated by the characters .r-, are energized from the secondary c'oil of the tran-sformer Tl as shown by the reference characters :v thereon.

Associated with each of the valve groups 6, 8, and l0 are resistors R|4, Rl5, R|'6, and R|| arranged in that order and in series circuit. The set of resistors Rl4, R|5, R|6, and RIT associated with the valve group 6 has end terminals |38 and |40, the set associated with the valve group 8, terminals` |42 and |44, and the set associated with the valve group I0 terminals |46 and |48. Ter--V minals |38, |40, |42, |44, |46, and |48 are connected respectively directly to the cathode of the valves |02, |04, |06, |08, H0, and H2 respectively by lead wires |50, |52, |54, |56, |58, and |60 respectively. The junctions between each of the resistors RI'5 and R|6 are connected together by a bus connection |62 and to the variable potential terminal I 64 of a potentiometer resistor PR2. One terminal of the resistor PR2 i-s connected to a minus potential source B3 such as the minus terminal of a battery, and the other end of the potentiometer resistor PR2 is connected to a ground terminal G2. Commutating condensers C5, C6, and C1 are respectively connected between the conductors |-|52, |54-|56, and |58-|60. An anode bus |66 is connected to each of the anodes of the valves |02, |04, |06, |08, H0, and H2 and tc the positive potential terminal BI. The junction between the resistors RM and R|5 of the set associated with the valve group 6 is connected to the common grid connection 56 by a conductor |68. The junction between the resistors R|6 and RH associated with the same valve group 6 is connected by means of a conductor |70 to the common grid connection 58. Similarly, the junctions between the other resistors R|4 and Ri 5 are connected t'o the common grid connections and 64 by conductors |12 and |24 respectively. Also similarly the junctions between the other resistors R|6 and RH are connected to the common grid connection 62 and 66 by conductors |16 and |18 respectively.

Referring specifically to the modification shown in Fig. 2, electrical energy is suitably inductively supplied to the star connected windings 200A, 200B, and 200C having a common junction 200D by suitable means not shown. Valve groups 206, 208, and 2|0 are associated with transformer units 2|2, 2|4, and 2|6 respectively, which transy former units are identical to the transformer units |2, |4, and I6 of Fig. 1 and have primary coils 2|2A, 2|2B, 2|2C; 2|4A, 2|4B, 2|4C; and 2 |6A, 2|6B, 2 |6C; and output coils 2 |2-0, 2 |4-0, and 2|6-0. The terminals of the windings 200A, 200B, 200C opposite the common junction 200D are connected to supply buses 2&8, 220, and 222 respectively. The bus 2|6 is connected tothe center tap connection of the primary coils 2|2A, 2 |4A, and 2|6A, the buses 220 and 222 being connected respectively to the primary coils 2|2B, 2|4B, and 2|6B; and 2|2C, 2|4C, and 2|6C. The valve groups 206, 208, and 2 l0 may be considered as comprising valve means units consisting of the electronic valves A of the various groups and a second of the valve means unit consisting of the electronic valves identified as B valves of the various groups. The left-hand end connections of each of the primary coils of the transformer units 2|2, 2|4, and 2|6 arel connected to the anodes of the A valves of the valve groups 206, 208, and 2| 0 respectively, while the right-hand end connections of the primary coils of the said transformer units are connected to the anodes of the B valves of the said valve groups respectively. All the cathodes of the A and B valves of each group are connected together and respectively to cathode buses 224, 226, and 228. The bus 224 is connected through an inductive reactu ance 230 to a bus 232, which bus 232 is connected to the common point 200D of the star-connected windings 200A, 206B, and 200C. Similarly the cathode buses 226 and 228 are connected to the bus 232 through inductive reactances 234 and 236 respectively.

The grids of the A valves of the units 206, 206, and2 I0 Aare connected through grid resistors R2 Il' tov respective common vgrid connections 238, 240, and 242. The grids of the B Valves of the units 206, 208, and 2|-0 are connected through grid resistors RIS respectively to common grid connections 244, 246, and .248. Corresponding end connections of the output coils 2| 2 0, 2| 4 0, and 2|6-0 are connected together while the opposite corresponding end connections of the said output coils are connected to output buses 250, 252, and 254 respectively.

The grids of the various units of A valves and B valves are rendered positive and negative with respect to their associatedcathodes by the control system |06 of Fig. 1 acting through a second set of electronic valves and transformers. For simplicity the control system |60 has not been shown in Fig. 2, but itis to be understood that it is associated therewith, and its connections to the circuits shown in Fig. 2 will be readily ascertainable inthat the conductors |68, |10, |12, |14, |16, and |13 of the circuit |06 are shown in their cooperative relationship with the additional circuitv elementsfshown in Fig. 2.

A transformer unit 260 has a center tapped secondary coil 262 having end connections 264 and 266 and a center tap connection 26S. End connection 264 is connected to the common grid connection 2318, while the end connection 266 is connected to the common grid connection 244. The center tap connection 268 is connected to the common cathode bus .224. The transformer 266 has a primary coil 210 having end terminals 212 and 214 and a center tap connection 216. A resistor RIS is connected across the terminals 212 and 214. The terminal 212 is connected to the anode of an electronic valve 218, while the terminal 214 is connected to the anode of an electronic valve 280. The valves 213 and 260 are preferably of the tetrode type having an anode, a cathode, a grid, ,and a screen grid, which screen grid acts to isolate the anode or plate from the `control grid. The screen .grids of the two valves 218 and 280 are connected together and to the center tap connection 216 of the primary coil 210. The .grid f the Valve 218 is connected through a grid resistor R20 to the conductor |68 which is the same conductor vas is shown in Fig. l.. The grid of the valve 280 is connected through a grid resistor R2| to the conductor |10 of Fig. 1. Similarly the valve groups 260 and 2|@ have transformers 262 and 264 respectively which are identical with the transformer 260 and are similarly connected to the common grid connections 240, 242, 246, 248, and the cathode buses 226 and 2218. The primary coils of the transformers 282 and 264 are connected similarly to the primary coil 210 of the transformer 260 to electronic tetrode valves 286, 286, 296, and 262, whose grids are connected through grid resistors R22, R23, R24, and R25 to conductors |12, |16, |14, and |16 respectively. All the cathodes of the valves 216, 280, 286, 288, 290, and 292 are connected to a cathode bus 264. All the screen grids of the said electronic valves are also connected together and to a bus 296. The bus 296 is maintained at a positive potential with respect to the bus 294 as by a battery 298.

The operation of the system shown in Fig. 1 is as follows: Assuming that the proper direct current potentials are applied between the terminals BI-GI, B2-GI, and B3-G2 and that a potential is being induced in the systems 2, 3, and 4, valve I I4 will oscillate, placing a pulsating poten- 8 tial vbetween ythe bus II8 .and -the bus |20. The potential so placed between .buses |I8 and |20 is not suiicient of itself to render the -potential of the grid suiiiciently elevated from its normal negative condition to permit the valves to lire, but when this potential is applied in conjunction with a poten-tial Ydeiined as the priming potential (which likewise is of itself insuicient to cause the valves to conduct), the two potentials ar-e suiiicient to cause the valve to conduct. Assume an operating condition wherein valves |04, |08, and I I0 are conducting and valve |02 is primed ready to be rendere-d conductive at the next pulse of potential between the buses ||8 and |20 induced by the transformer T2. Current flowing through the valve |04 raises the potential of the junction point between the .resistor R6 and resistor R1 associated therewith, .and this increased potential is conducted by the conductor |34 to the grid of the valve IIB to maintain the valve ||0 primed. Current flow through the conductive valve IIB raises the potential of the junction of the resistor R6 and R1 associated therewith, and this raised potential is conducted by means of conductor |32 to the grid of the valve |08 to maintain the valve |08 primed. The conduction of current through the valve |08 raises the potential of the junction point between Ythe resistors R6 and R1 associated therewith, which increased potential is conducted by means of conductor |26 to the grid of the valve |02, which is not conducting, to prime valve |02. Conducting valve |04 was not primed and will become nonconductive at the next cycle of valve I |4. The transformer T2 places a potential pulse between the buses ||8 and I20, which is of itself insuicient to cause any of the grids to become enough positive with respect to their associated cathodes to cause the valve to conduct, but when such pulse is applied to a grid which has been primed or partially raised in potential with respect to its associated cathode it is suilicient to raise the potential of the grid to cause the valve to become conductive. Therefore, at th'e next oscillation of the valve ||4 which will induce a potential of the correct polarity between the buses I I8 and |20, the primed valve |02 will be rendered conductive. During the time valve |04 was conducting, the commutating condenser C5 was in a lcharged condition in which the `condenser terminal connected to the conductor |52, and thereby to th'e cathode 0f valve |04, was at a positive p0- tential differing only by the internal potential drop of valve |04 from the positive potential of bus |66; and the condenser terminal connected to the conductor |50, and thereby to the cathode of valve I 02, was at the potential of cathode bus |20 or at a negative potential so that substantially the entire potential appearing between Bl and Gl appeared across condenser C5. When valve |02 became conductive, the cathode thereof and conductor |50 increased in potential to a positive potential differing only from the positive potential of bus |66 by the internal potential drop of valve |02. This transitorily raised the potential of the terminal of condenser C5 connected to conductor |52 and that of the cathode of valve |64 an amount equal to the increase of the other terminal.. Since the cathode of valve |04 was originally operating substantially at anode potential or the potential of bus |66, the cathode potential will be raised substantially above t-h'e anode potential and valve |04 will immediately be rendered nonconductive. The capacity of condenser C5 is such that the duration of the transient is sufficient to permit valve |04 to deionize.

Current conducted by' the valve |02 raises the potential of the junction between the resistors R6 and Rl associated therewith, which increased potential is `conducted by means of conductor |35 to the grid of the valve ||2, thereby priming the same, so that at the next potential pulse of the transformer T2 on the buses ||8 and |20, the valve 2 will be rendered conductive, and, by means of the commutating condenser C1, valve I I will be rendered nonconductive. In like manner, each time one of the valves |02, |04, |06, |06, ||0, and I I2 is rendered conductive, it primes another of said valves and, due to the .commutating action of the condensers C5, C6, and Cl, will render the valve, associated with the newly conductive valve, nonconducting. The valves |02, |04, |06, |08, IIU, |I2 are so interconnected with each other that they fire in the order of valves |02, II2, |06, |04, IIO, and |08 and in a timed relation whereby each valve is rendered conductive sixty electrical degrees after the preceding valve is rendered conductive to provide for a three-phase output.

When the valve I 02 is not conducting, the potential of its cathode and of the terminal |38 is substantially that of terminal GI. When the valve |02 is conducting, the potential of its cathode and of terminal |38 varies from the potential of the anode and terminal BI 4by only the internal drop in the valve. Consequently, the

conductor |58 and common grid connection 56 will be positive with respect to bus |82 -when valve |02 is conducting and negative with respect to the bus |62 when the valve |02 is nonconducting. With the grids of the valves 6A, 6B, and

6C rendered positive with respect to their cathodes, they become conductive, and current flows from the windings 2A, 2B, and 2C through the conductors I3, 20, and 22 respectively, the lefthand side of the coils |2A, I 2B, and I2C, the common bus 36, and the inductive reactor 2R bacl; to the common junction 2D. This current ilow through the coil |2A, IZB, and I2C sets up a flux in the iron of the transformer unit I2 to induce a voltage of one polarity in the output coil |2-0. While this is occurring valve I|2 will be rendered conductive to act in a manner similar to that described with respect to valve |02 to render the valves |8D, IBE, and |011' conductive, causing current to ilow from the windings 4A, 4B, and 4C through conductors 38, 32, and 34 and the righthand half of the coils ISA, ISB, and ISC whereby a ilux is induced in the iron of the transformer unit I 6 which induces a voltage in the output coil IB-il displaced 120 from that being induced in the output coil |2-0 of the transformer unit I2. At the instant thc valve |I2 was rendered conductive, the valve ||0 was rendered nonconductive, so that only one of the common grid connections 66 or 64 will be a positive with respect to the cathode bus 32. At the next cycle of the valve II4, the valve |06 will be rendered conductive and the valve |08 will become nonconductive whereby the potential of the common grid connection 60 is raised and the potential of the common grid connection 62 is lowered with respect to the common cathode bus 36 for rendering the valves 8A, 8B, andBC conductive. Current will then flow from the coils 3A, 3B, and 3C to the conductors 24, 26, and 28 respectively and through the lefthand half of the primary coils |4A, |4B, and |4C, setting up a iluX in the transformer unit I4 which causes a voltage to be induced in the output coil |4-0 thereof and which will be displaced 120 from the voltage being induced in the coil |6-0. Similarly, at the neXt cycle of th valve II4, valve |04 will be rendered conductive and valve |02 will be rendered nonconductive, which action will raise the potential of the com'-v mon grid connection 58 and lower the potential of the common grid connection 56 with respect to the common cathode bus St. This will cause the valves 6D, 6E, and 6F to conduct current from the windings 2A, 2B, and 2C through conductors I8, 20, and 22 through the right-hand half of the primary coils IZA, |2B, and I 2C setting up a ilux in the iron of the transformer unit |2 in a direction to induce a voltage in the output coil |'2-0 displaced 120 from the Voltage being induced in the coil 4 0.

Each of the valve groups 6, 8, and I0, transformers I2, I4, and I6, reactors 2R, 3R, and 4R, and systems 2, 3, and 4 operate in the same manner and a detailed description of one will serve for all.

Assume an instant in which the valves 6A, 6B, and 6C have their controlling grids positively biased and the conductor I8 is more positive than conductors 20 and 22 so that valve 6A is conducting. Current flow through the left-hand half of coil IZA will set up a certain flux in the core of the transformer I2 causing an instantaneous voltage across the left-hand half of the coil I2A opposite in polarity to that of the instantaneous voltage in conductor I8 and such that the center point of the tranformer will be positive with respect to the anode of the valve 6A. Instantaneous voltages of equal magnitude and polarity to that in the left-hand half of coil I2A will be set up by the flux in the left-hand valves of the coils |2B and I2C. As the instantaneous voltages in conductor I8 decrease, the voltage of conductor 20, which is electrical degrees behind that of conductor I8, becomes more positive. When these voltages are equal, Valve 6B commences to conduct and the instantaneous voltage in the left-hand half of coil |2B increases along with the increasing voltage in conductor 20 in the same manner as coil I2A when valve 6A was conducting, causing the voltages in the left-hand halves of the coils |2A and I2C likewise to increase. Since the voltage in the left-hand half of the coil Il2A is of opposite polarity to that of the phase 2A and is increasing while the voltage of phase 2A is decreasing, the voltage drop across the valve 6A rapidly decreases below that necessary to sustain conduction through the valve 6A and consequently the valve 6A is rendered nonconductiveA Similarly the voltage of conductor 20 reaches a positive peak and then decreases. As this positive voltage decreases, the positive voltage of conductor 22 increases until it becomes equal to the positive voltage of conductor 20, at which time valve EC commences to conduct, increasing the voltages of the left-hand half of the coils |2A, IZB, and I2C, causing the valve 6B to be rendered nonconductive in the same manner valve `6A was rendered nonconductive by the conduction of valve =6B. Similarly, at a later instant the voltage of conductor 22 decreases and that of conductor I8 increases, causing valve 6A to conduct again and valve 6C to be rendered nonconductive.

Assume now that the grids of the valves 6D, 6E, land 6F have just been positively biased and the grids of the valves 6A, 6B, and `EC have just been negatively biased and, further, that conductor I8 is more positive than conductors 20 and. 22 and that valve EA is conducting, It will be appreciated that due to the conduction of valve 6A, the

il right-hand side of the associated condenser C'Iv andanode of valve 6D are highly positive Withrespect to the anode f valve 6A because of the voltage across the coil' I2A. Therefore, as soon 'as the grid of valve 6D is biased positively, valve 6D conducts and the voltage of its anode is immediately lowered to substantially that of its cathode, differing therefrom by only the voltage drop. of the valve 6D. Because the charge on the -commutating condenser C'I could` not leak off instantaneously, the anode of. the valve 6A iscaused transitorily to be lowered in potential an equal amount, which made the potential of the anode of' valve '6A negative with respect to its cathode and rendered the valve 6A nonconductive. Since the grids of the valves 6A, 6B, and.A 6C `are now negatively biased, these valves will remain nonconductive. Since the center tap of the coil I'2A is of lesser positive potential than the end thereof connected to the anode of. the valve 6D and if the cathodev of the valve 6D was maintained at the potential' of the common point 2D, the potential of' conductor I8 would be. transitorily lowered to ay negative potential and a heavy transient current would occur in the system. The reactor 2R acts under these conditions to transitorily permit the relative potential between the cathode connection 36 and the point 29 to vary. Since the potential ofthe connectionv 36 is held at ground potential, the eiect of the reactor 2R is to lower the potential of the common point 2U and of the center tap of coil IZA and anode of valve, 61) thereby reducing thev heavy transient; or surge currentthrough phase 2A. The inductance of reactor 2R is preferably related, to the capacitance of' condenser-so that the charge across the reactor 2R disappears substantially as the charge leaks oit' of" the condenser-through the. coil I'ZA, and the transformer reverses polarity so that the potentialV of the center tap :connection of the coil IZA increases.

Continued oscillation of the valve II4 will` sequentially render valve III] conductive, Valve I|2 nonconductive, valve |08- conductive, valve |'06` nonfconductive, valve |132 conductive, and' valve Ille noncon'ductive inA a manner already described. `It will be evident therefore that a threephase powerl output supply is produced in the conductors t, 5 2, and 54 in which the conductor 50* is phase if, conductor 52 phase 2; and conductor 5'4 phase 3. It should be noted' that in this form of the invention the bus 36 connectsall thecathodes of the valvesV in groups 6, 8, and IIl; so that all the cat'hodes remain at a common potential, which may be conveniently grounded to the frameof the machine with which this apparatus is associated or to actual ground, so that a person coming inv contact with any of the conductors wouldv not be shockedI thereby. The common points 2D, 3D, and 4D, however, are variable inpotential and float with respect to the potential of the cathode bus 36 due to the variable dropy across the inductive reactorsA 2R 3R, and 4R.

The modification shown inA Fig- 24 works simi.- larly to the form shown inl Fig. 1, except that the cathode-buses 224, 226, and 228 are tied together through the inductive reactors 230; 234", and 23d so that the potential-ofthebus 232remains constant with` respect to all the units and may be grounded, if desired, whilel the potentials of the variousicathod'e buses 224i, 2261, and; 2F28 float with respect to the potential ofv` the bus 2%2y dueto the variable potential drop-across the inductive reactors 23131, 21M?, andE 236 Since the relative potentials of' the cathode buses 224",y 226, Iand 228' arel not constant, it is necessary to. insert between the control unitv me andthe common cathode connection for the valve, units 2061 Zilgand' 21H1 addi.. tional apparatus whereby the variation or floating,v of the potentials ofthe cathode buses 224; 2216, and 228' will have no effect upzon the opera'- tion of the control system.

As. explained with. respect to the form ofthe invention shown in Fig.. l, the potentials of the conductors IIi, INI, l2', I`l6`; |14, |.1T8'with respect. to the potential of the conductor |62 are periodically changedv so that the conductors |18", |12, ITD, VM,v |76, and. IGB are rendered. positive in potential with respect to the conductor IS' in sequence. and in the aforesaid order., This, rendering of the conductor positive with respect t'o conductor I'6`2will render the grids of the vallves 292',` 286 ZSEL. 299 288', and 27S sequentiallyv in that order positive .withrespect tothe cathodes of the said valves. so that said' valves will" become conductive. When the valve 28ers renderedconductive, current will flow fromy the positive terminal` of the battery 298 through the bus 296 througiiv the right-hand' half of th'e primary coil 2210, the Valve 280 to the common cathode bus 29A back to the negative terminal of the battery 2&8. This-Will induce a flux in the iron core of the transformer 260, which in turn induces a voltage in the secondary lcoil 262' which has its polarity so arranged that lwhen the. right-hand half of the primary coil 210 is conductive, the common grid.. connection 244 will. be rendered positive with respectv to the. commonv cathode bus 224, whereby the B`valvesof'the group 206` will'be renderedconductive and a voltage. will' be induced in the output coil 212-0 as described in connection with the form shown. in Fig. 1.. Similarly, when the valve 2THA is conducting,v current flows from the battery 238 to the left-hand. portion of the primary coilv 216). of the transformer. 258 through the valve 278i back to the battery 298 whereby a voltage is induced in thev second'- ary coil4 262 of such polarity that the common grid connection 238' is rendered positive with respect. to the common cathode Iconnection 224', and the valvesv A of the valve group 206' willn be rendered' conductive. The valves 288,. 286, 292', and 29.5 will similarly render the common grid connections 245, 24B, 248, and 242 positive with respect to the common cathode connections. associated `with thecommon grid connections.. From analogy with the. forms shown in Fig. 1, the conductors 250', 252, and 254; form` respectively the first, second, and third phases of a three-phase output circuit having a frequency of,l one-sixth that of' the frequency oithe oscillation of.l theV control os-cillatorvalve H4'.

Although two preferred embodiments of the invention* have been described in detail,` it will' be appreciated that various, modifications in the form, number, and arrangement of the parts may be made without departing from the spirit and scope of the-invention.

What is claimed and is: desired' to be secured by Unitedy States Letters Patent, is as follows:

1`. In a system for. transferring electrical energy from a multiphase input circuit to a load circut, a plurality of' valve means` havinga common cathode connection andy grid means. andv a plurality of anodes, translatingmeans having a plurality of input circuits' and an outputY circuit, each of said input circuits comprising., a current input connection and a pair of current. output' connections, circuit meansl connecting each of said current input connections to certain of the phases of said input circuit, circuit means connecting said current output connections to said anodes, means connecting said cathode connection to said input circuit, means connecting said output circuit to said load circuit, and means for periodically biasing said grid means with respect to said common cathode connections.

2. In a system for transferring electrical energy from a multiphase input circuit to a load circuit, a pair of valve means, each of said means having a common cathode connection and grid means and a plurality of anodes, translating means having a plurality of input circuits and an output circuit, each of said input circuits comprising a current input connection and a pair of current output connections, circuit means connecting each of said current input connections to certain of the phases of said input circuit, circuit means connecting corresponding ones of said current output connections to said anodes of one of said pair of valve means, circuit means connecting the other corresponding ones of said current output connections to said anodes of the other of said pair of valve means, means connecting said cathode connections to said input circuit, means connecting said output circuit to Said load circuit, and means for sequentially biasing each `of said grid means with respect to its associated common cathode connections.

3. In a system for transferring electrical energy from a multiphase input circuit to a load circuit, a pair of valve means, each of said means having a common cathode connection and grid means and a plurality of anodes, translating means having a plurality of input circuits and an output circuit, each of said input circuits comprising a current input connection and a pair of current output connections, circuit means connecting each of said current input connections to certain of the phases of said input circuit, circuit means connecting corresponding ones of said current output connections to said anodes of one of said pair of valve means, circuit means connecting the other corresponding ones of said current output connections to said anodes of the other of said pair of valve means, means connecting said cathode connections together, an impedance means, circuit means connecting said common cathodes to said impedance means and said impedance means to said input circuit, means connecting said output circuit to said load circuit, and means for sequentially biasing each of said grid means with respect to its associated common cathode connections.

4. In a system for transferring electrical energy from a multiphase 4input circuit to a load circuit, a plurality of pairs of valve means, each pair including two anodes and two grids and a common cathode connection, translating means having a plurality of input circuits and an output connection, each input circuit having opposite end connections and a center tap connection, means connecting respective phases of said input circuit to said center tap connection, means connecting respective opposite end connections to the respective anodes of each pair of valve means, a common grid connection for the corresponding grid of each of the corresponding pairs of valve means, a second common grid connection for the other of the corresponding grid of the pairs of valve means, and means for sequentially biasing the respective common grid connection with respect to the common cathode connection.

5. In a system for transferring electrical energy from a multiphase input circuit to a load circuit, a plurality of pairs of valve means, each pair including two anodes and two grids and a common cathode connection, transformer means having a plurality of separate input coils and an output coil, each input coil having opposite end connections and a center tap connection, means connecting respective phases of said input circuit to said center tap connection, means connecting respective opposite end connections to the respective anodes of each pair of valve means, a common grid connection for the corresponding grid of each of the corresponding pairs of valve means, a second common grid connection for the other of the corresponding grid of the pairs of valve means, and means for sequentially biasing the respective common grid connection with respect to the common cathode connection.

6. In a system for transferring electrical energy from a multiphase input circuit to a multiphase load circuit, a plurality of groups of electric valve means, a translating means for each group of valve means, each translating means comprising an output coil and a plurality of center tapped input coils having end connections, circuit means connecting certain phases of said source to said center taps of the input coils of each translating means, each said group of valve means comprising a pair of valve means, each said pair of valve means having a common cathode connection and a common grid connection and anode means, means connecting corresponding end connections of the input coils of the corresponding one of said translating means to the anode means of one of said pair of valve means of the corresponding group of valve means, circuit means connecting the other corresponding end connections of the input coils of the corresponding one of said translating means to the anode means of the other pair of said valve means of the corresponding group of valve means, and means for sequentially biasing the respective common grid connections, and circuit means connecting the output coils of each translating means to a multiphase load circuit.

7. In a system for transferring electrical energy from a multiphase input circuit to a multiphase load circuit, a plurality of groups of electric valve means, a translating means for each group of valve means, each translating means comprising a single core inductive element having an -output coil and a plurality of center tapped input coils with end connections, circuit means connecting certain phases of said source to said center taps of the input coils of each translating means, each said group of valve means comprising a pair of valve means, each said pair of valve means having a common cathode connection and a common grid connection and anode means, means connecting corresponding end connections of the input coils of the corresponding one of said translating means to the anode means of one of said pair of valve means of the corresponding group of valve means, circuit means connecting the other corresponding end connections of the input coils of the corresponding one of said translating means to the anode means of the other pair of said valve means of the corresponding group of valve means, and means for sequentially biasing the respective common grid connections, and circuit means connecting the output coils of each translating means to a multiphase load circuit.

8. yIn a system for transferring electrical energy from a multiphase input circuit to a multipliase necti'ons andof a number-equal to one-half the y number of anodes of the group of valve lmeans l"to 'which -it lis connected, vcircuit means vconnecting phases of said source -to eachof saidcenter ftaps, 'each said group `of valve 'means comprising a :pair of valve means, each said pair of valve means having a common cathode connection and A-alcomnion grid connection and the same number o`f1anodes as there are groups of valve means, fmeans connecting corresponding end connections "of-thc inputcoils of the-corresponding one of said transformer means to the anodes-of one of said 'pair-of valve means of the correspondnggroup 'of valve means, circuit means connecting `the "other corresponding end connections of ythe in- I'plit'coils of the correspon-ding one of said trans-- i-ormermeans to the -anodes of the other pair of rsaid valve means of xthe corresponding groupof `valve means, and means for sequentially .biasing the respective common grid-connections of Veach vgroupcf valve-means, an-d circuit means connectfin'g the output coils of each translating means to a-multiphase loa-d circuit.

9. 'In la system for transferring electrical energy vfrom a mul-tiphase input circuit to a multip'hase load circuit, a plurality of groups of electric Valvemeans-of the same numberas the phases vin said lo'ad circuit, a transformer means for each "group of -valve means, each transformer `means `comprising a vsingle core having an output coil vanda vplurality of center tapped input coils with end connections and of -a number equal tothe vnuniberof phases of said source, circuitmeans `connecting .a different phase of said source to each 'of said center tapsof one of said transforming mean'sfcircuit means correspondingly connecting eachiof the other of said transformer means to ssa-idfs'ource, each said group of valve means comprising a pair'of valve means, each said pair 'of valve means having a common cathode connec- "tionand-a common grid connection and a plurality of anodes, means connecting corresponding end connections of said input coils of the correisponding one of said transformer means to the anodes of 'one of sai-d paire-f valve means of the corresponding group of valve means, circuit Pmeans connecting the-other corresponding end Iconnections of the input coils of the corresponding one of -said transformer `means tothe anodes of 'the-other pair of said valve means of the corresponding group of valve means, and means for sequentially bias-ing :the respective common vgrid 'connection-s of each group of valve means, and vcircuitmeans connecting the output coils of each Itranslating-meansto fform a multiphase load crcuit.

10. In a system `for transferring Ielectricalfen- -ergy from a multipli-ase input circuit to a multiphase load circuit, a plurality of groups -of'elecgtricvalve means of the same number asthe'phases 'in saidload'circuitya'transformer means for each group 'of Valve means, each transformer means 'comprising asi'ngle'core'having an output'coil and apluraiity of center tapped input coils with 'end .connections and of a number equal tothe number of phases of said source, circuit -means connecting a different phase of said source to Veach of said center taps of one of said ,transforming means circuit means correspondingly connecting `each 'of the i other of said transformer means @to 'said source, each said group'o'f lvalvemeans'comffprising a pair =of valve means, -eac'h said ,pai-ref valve means `having a common-cathode conneclmeans lconnecting -the other corresponding end connections/of the input coilsof thecorresponding one of said transformer means to the anodes of the otherpairof said valve means-of the corresponding group of val-ve means, andl means 'for biasing the respective common grid connections of each group of valve means alternately 'andin predetermined relation with respect to each lof said vother groups, and circuit means connecting the output coils'of each translating means toform a multiphase'load circuit.

li. "In a system for .transferring electrical-energy 'from'a Vmultipliase input circuit to a `multiphase load circuit, a plurality of groups of electric valve means of the same number as the phases insa-id load-circuit, a transformermeansfor each group yof valve means, each transformer means comprisinga single core having an output coil and a plurality of center tapped inputcoils with end connections and of a number equal tdthenumber ci' phases-of said source, circuit means connecting a different phase of said source to eachof said center taps of one of said transforming means, circuit means correspondingly*connecting eachof vthe other of said transformer means to said 'ing the other "corresponding end connections of the input coils of the corresponding one of said transformer means tothe anodes'of the other pair lof said valve means of the-corresponding group'o'f valve means, and means for'sequentially'biasing the respective common grid connections ofeach -group of valve means, a separate impedance element for each Yof said-groups of valve means, circuit means connecting said common cathode connections of each of said groups to one terminal of the one of said impedance element 'associated therewith, circuit means connecting the other terminals of said vimpedance `elements together land to said source'an'd circuit means connecting `the output coils 'of each translating means Ato form a multiphase load circuit.

12. In a system for transferring electrical energy from a multipliase input system to a'multiphase load system, a plurality ofgroups 'of valve 'means corresponding in number to thenumber of phases in the load system, each group having a separate translating means, each group of vvalve means comprising a pair of valve means, each pair of valve means comprising a plurality of anode's an-d a common cathode connection and a common grid connection, circuit Vmeans connecting all .of

`said common cathode connections together, each translatingmeans having a plurality of input connections and an output connection, circuit means connecting .certain of said input lconnections t'o correspoding phases of `said input source, vcircuit lmeans connecting certain other of said input connections to the anodes of one oi said valve means, circuit means connecting certain other of said input connections to the anodes of certain other of said valve means, and circuit means connecting said ,translating means output connections to the load system.

13. In a system for transferring electrical energy from a multiphase input system to a multiphase load system, a plurality of groups of valve means corresponding in number to the number of phases in the load system, each group having a separate translating means, each group of valve means comprising a pair oi" valve means, each pair of valve means comprising a plurality of anodes and a common cathode connection and a common grid connection, circuit means connecting all of said common cathode connections together, each translating means having a plurality of input connections and a pair of output connections, circuit means connecting certain of said input connections to phases of said input source, circuit means connecting certain other of said input connections to the anodes oi one oi said valve means, circuit means connecting certain other of said input connections to the anodes or" certain other of said valve means, circuit means connecting corresponding ones of said pairs of output connections together, and means connecting the other corresponding ones of said pairs of output connections to said load system.

14. In a power transferring system, a plurality of multiphase electrical energy input circuits electrically isolated from each other, a pair of valve means for each multiphase source, each of said valve means comprising a common cathode connection and a common grid connection and a plurality of anodes, a translating means for each of said multiphase sources, each oi said translating means comprising a plurality oi input circuits and a load circuit, each of said input circuits having opposite end connections and a center connection, circuit means connecting certain phases of the respective multiphase sources to said center tap connections, circuit means connecting corresponding end connections of said input circuits to the anodes of corresponding ones of said pairs of valve means, circuit means connecting the other end connections of the respective input circuits to the anodes of the corresponding other ones of said pairs of valve means, circuit means for iiow of current from said common cathode connections to the one of said multiphase sources to which the co-operating anodes of said common cathode connections are connected, and circuit means for connecting the output circuits of said translating means to the load circuit.

15. In a power transferring system, a plurality of multiphase electrical energy input circuits electrically isolated from each other, a pair of valve means for each multiphase source, each pair having common cathode connections, each of said valve means comprising a common grid connection and a plurality of anodes, a translating means for each of said multiphase sources, each of said translating means comprising a plurality of input circuits and a load circuit, each of said input circuits having opposite end connections and a center connection, circuit means connecting certain phases of the respective multiphase sources to said center tap connections, circuit means connecting corresponding end connections of said input circuits to the anodes of corresponding ones of said pairs of valve means, circuit means connecting the other end connections of the respective input circuits to the anodes of the corresponding other ones oi said pairs of valve means, circuit means for flow of current from said common cathode connections to the corresponding one of said multiphase sources to which the corresponding valve means are connected, and circuit means for connecting the output circuits of said translating means to the load circuit.

16. In a system for controlling iiow of electrical energy between a source and a multiphase load circuit, a plurality cf networks, each network being individual to a phase of the load circuit and having an output circuit controlling such phase, a single controlling pulsating source for operating said networks, each network comprising a pair of valve means alternately rendered conductive for controlling the alternating flow of energy in the phase of the load circuit controlled by such network, and means interconnecting said networks whereby the potential supplied by the conducting one of said pair of valve means of one network prepare-s a nonconducting one of another of said pair of valve means in another network whereby said nonconducting valve means may be rendered conductive at the next pulse of said single source.

1'?. In a system for controlling now of electrical energy b-etween a source and a multiphase load circuit, a plurality of networks, each network being individual to a phase of the load circuit and having an output circuit controlling such phase, a single controlling pulsating source for operating said networks, each network comprising a pair of valve means alternately rendered conductive for controlling the alternating fiow of energy in the phase of the load circuit controlled by such network, means interconnecting said networks whereby the potential supplied by the conducting one of said pair of valve means of one network prepares a nonconducting one of another of said pair of valve means in another network whereby said nonconducting valve means may be rendered conductive at the next pulse of said single source, and means actuated by the one of said valve means of said pair of valve means as it becomes conductive for rendering nonconductive the other of said valve means of said same pair of valve means.

18. In a system for controlling flow of electrical energy between a source and a multiphase load circuit, a plurality of networks, each network being individual to a phase of the load circuit and having an output circuit controlling such phase, a single controlling pulsating source for operating said networks, each network comprising a pair oi valve means alternately rendered conductive for controlling the alternating ilow of energy in the phase of the load circuit controlled by such network, each or said valve means having cathodes, means interconnecting said networks whereby the potential supplied by the conducting one of said pair oi valve means of one network prepares a nonconducting one of another of said pair of valve means in another network whereby said nonconducting valve means may be rendered conductive at the next pulse of said single source, and means interconnecting the cathodes of said valve means of each of said pairs of valve means whereby the newly rendered conductive one of said valve means oi said pair of valve means will render nonconductive the other of said valve means of said same pair of valve means.

19. In a system for controlling now or electrical energy between a source and a multiphase load eireuta control means -for,sunisliiinsfa'pnlsating ing ,an .anode .and .a grid and v.a cathode, .-a-.iirst t.

circuit gfor `supplying a yIpnosi-tive potential .to said anodes anda negative potenti/al :to ,said .Cathodes,

a second circuit for impressing said pulsa-ting potential between said grids and said cathodes, said .pulsating potential being .of itself .insufficient .to Vcause :said :valve means st o ibe menderesd `.conductive, and means associated `With ,each l.of `said valve means .and operable lupon ,conduction of the valve ymeans v with which it Vis .associated .to raise the vpotential of the ,grid of .anotherof said valve means vwhereby said pulsating lpotential will render saidanother valve meansconductive.

A20. In a system -for controlling flow of .electrical energy between a Vsoulrce `and Va Arnultiphase fload eircuaa control means .for supplying apulsaiing potential, a pair of valve .means -ior .controlling the Af lotvof energy from said source to each .phase of said load circuit, each ,of ,said vvalve means having an anode and .a Jgrid and 'a cathode, na irst circuit for supplying a positive .potential vto said anodes and a negative .potential rto said cathodes, a second circuit for impressing said pulsating potential ,between said .grids .and said cathodes, said .pulsating potential :being of itself insufficient to cause said valve means to ,be rendered conductive, .and means associated with each of said 4.Valve means and .operable upon conduction -of the valve means with which it .is a-sso eiatecl yto raise vthe potentialof-the grid of another of the-valve means `of another vof said pair of valve vmeans whereby said pulsating potential Will render .said .another valve means conductive.

ESO

21,,lnga'systernorcontrollingflow of electrical energy between a source and a multiphase `load feircuit., .azeontzro1-means afer supplying a pulsating potential, a g-pair of `valve lmeans for ycontrolling the iiowloffenelylam said source to each phase of :said Llo'ad eireuin each Aof Vsaid valve means having an anode and a gridgand a cathode, a rst -circnit forsupplying a `positive potential to said anodes and s anegative potential to said .c'athodes, a second circuit fior impressing said ,pulsating PQUQHLQJ betwensaidzgrids and said cathodes, said pulsating Ipotential being .of itself insuilcient to :cause .said vali/2e .means :to he .rendered conductive, Ineans assodated -Wi'th .each of said valve means and :Operable:llDQrlcondllction .of the 'valve :means with -W11.ieh it is :associated to raise the :grid potential-of another valve means of another A0f.said:pai-1" :of Malvemeans .whereby said pulsating potential -will-rendersaid another valve means conductive', ,and .means .operable yupon .said an- .Qthelrvalvemeans becoming conductive to render nononductive :the valve vmeans Apaired with Said .e n other lvalve means.

GMjER vBOWLUSl The :following references .are of record in .the :file v,of :this patent:

UNITED STATES PATENTS Number 'Name Date .1.,9.55,'524 .Augier et a1.. v Apr. 17, 1934 1;9,5 ,18,8 W1l;i s v May 15, 1934 2,288,362 LMcArthurnr". June 30, '1942 

